nvmet: pci-epf: move DMA initialization to EPC init callback

nvmet: pci-epf: move DMA initialization to EPC init callback

For DMA initialization to work across all EPC drivers, the DMA
initialization has to be done in the .init() callback.

This is because not all EPC drivers will have a refclock (which is often
needed to access registers of a DMA controller embedded in a PCIe
controller) at the time the .bind() callback is called.

However, all EPC drivers are guaranteed to have a refclock by the time
the .init() callback is called.

Thus, move the DMA initialization to the .init() callback.

This change was already done for other EPF drivers in
commit 60bd3e039aa2 ("PCI: endpoint: pci-epf-{mhi/test}: Move DMA
initialization to EPC init callback").

Cc: stable@vger.kernel.org
Fixes: 0faa0fe6f90e ("nvmet: New NVMe PCI endpoint function target driver")
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Keith Busch <kbusch@kernel.org>